1. Field of the Invention
This invention relates to a hand instrument used in orthodontic procedures for removing brackets from teeth. More particularly, the present invention relates to a hand instrument for detaching adhesively bonded orthodontic brackets from teeth as well as methods for detaching orthodontic brackets from teeth.
2. Description of the Related Art
Orthodontic treatment is directed to movement of malpositioned teeth to improved positions in the oral cavity. Orthodontic treatment can greatly enhance the patient's facial appearance, especially in areas near the front of the patient's mouth. Orthodontic treatment can also improve the patient's occlusion so that the teeth function better with each other during mastication.
One type of orthodontic treatment involves the use of a set of appliances and archwires that are commonly known collectively as “braces”. During treatment, tiny slotted appliances known as brackets are affixed to the patient's anterior, cuspid and bicuspid teeth, and an archwire is placed in the slot of each bracket. The archwire forms a track to guide movement of the teeth to orthodontically correct positions. Ends of the archwire are often received in the passages of small appliances known as buccal tubes that are affixed to the patient's molar teeth.
In the past, orthodontic brackets were commonly welded or brazed to bands that were placed around the teeth. Today, orthodontic brackets are often bonded directly to the enamel surface of the teeth by an adhesive. Once treatment has been completed, the archwire is removed from the slots of the brackets and each bracket is then removed from the associated tooth.
Orthodontic brackets are typically made of metal, ceramic or plastic. Improved ceramic brackets are described in U.S. Pat. Nos. 5,439,379 and 5,366,372. The ceramic brackets described in those patents have two sections that are spaced apart from each other by a channel. In some of the embodiments described in those patents, the bracket sections are connected to each other by a thin web of material that lies along the bottom of the channel and contacts a layer of adhesive that bonds the bracket to the tooth.
The brackets that are shown in U.S. Pat. Nos. 5,439,379 and 5,366,372 are debonded from the surface of the teeth at the conclusion of treatment by urging the sections in directions toward each other. Hand instruments that are especially useful for debonding such brackets are described in those patents as well as in U.S. Pat. No. 6,474,988. The hand instruments include wall portions for engaging the sides of the bracket so that the sections of the bracket pivot toward each other and away from the tooth surface when handles of the hand instrument are squeezed together.
U.S. Patent Publication No. 2006/0127835 describes another hand instrument for detaching orthodontic brackets from teeth. The hand instrument illustrated in this reference includes two jaws, each of which includes a contact pad for engaging opposite sides of the bracket. When the jaws are moved together, at least a majority of the area of each contact pad is located beneath the archwire slot of the bracket in a lingual direction in order to facilitate fracture of the adhesive bond and release of the bracket from the tooth surface.
Some orthodontic brackets, such as ceramic brackets, are made of materials that are relatively brittle. Consequently, care must be taken during a debonding procedure to ensure that any portions of the bracket that break away from remaining portions of the bracket do not drop into the oral cavity. It can be a time-consuming task for the orthodontic practitioner to find and retrieve loose fragments of brackets that are of a small size, especially when made of translucent or transparent materials.